Bridge measuring method of active impedance of crystal oscillator circuits
Masahiro Toki, Shinichi Hattori, Hirokazu Nakano · Electronics and Communications in Japan (Part II Electronics) · 1989
Abstract Crystal oscillator circuits have been used widely in such electronic equipment as communication devices and measurement instruments. However, until the crystal is connected, usually it is uncertain if the circuit oscillates or it is difficult to determine how one adjusts the circuit for a desired oscillation frequency. With a view to alleviating these situations and improving the design method for the crystal oscillator circuits, a method is developed for accurately measuring with a bridge the two‐terminal impedance (equivalent series capacitance and negative resistance) of the active circuit seen from the connecting terminal of the crystal. A bridge measurement method for the small‐signal negative resistance related to the starting characteristics of the oscillator is discussed. In conjunction with the bridge measurement developed earlier for large signal operations under oscillation, a complete bridge measurement has become possible from the small signal region to the large signal region. The present bridge measurement method is useful in providing a basic specification for the active circuit side for a given crystal. It is also shown that the present bridge method is useful for evaluation of accuracy of other measurement instruments such as impedance analyzers.